Islamic State militants use 'poisonous substances' in village shelling; US strikes chemical weapons sites

More than 40 people have suffered partial choking and skin irritation in northern Iraq after Islamic State militants fired mortar shells and Katyusha rockets filled with "poisonous substances" into their village, local officials say.

None of the affected died, but five of them remain in hospital, according to health officials in Taza, a mainly Shiite Turkmen village 20 kilometres south of the oil city of Kirkuk, in a region under Kurdish control.

"There were poisonous substances in these shells. We don't know what," Kirkuk province governor Najmuddin Kareem told reporters on a visit to the village on Wednesday.

A total of 24 shells and rockets were fired into Taza from the nearby Bashir area, said Wasta Rasul, a commander of the Kurdish Peshmerga forces in the region.

The attack came as CNN reported that US aircraft had begun targeting the Islamic State group's chemical weapons sites near Mosul in Iraq, in an initial round of air strikes aimed at diminishing the militant group's ability to use mustard gas.

An Islamic State detainee provided vital information that allowed the US military to conduct the strikes, CNN said.

The ultra-hardline Sunni Muslim group seized large swathes of territory in northern and western Iraq in 2014.

"Daesh wants to scare off the population," said Kareem, using an Arabic acronym for the militant group.

"They want to show they have chemical weapons just like the previous regime," he said, referring to the chemical bombing of the Kurdish village of Halabja by Saddam Hussein's forces in 1988, which left thousands of people dead.